Abstract

The Arctic is experiencing a rapid rate of climate change and this is expected to continue over the next few decades. Particularly vulnerable aspects of the Arctic climate system is the rapidly declining sea-ice and the methane hydrates stored in the ocean sediments. The melting sea-ice could lead to a shutdown of the thermohaline circulation that brings heat to Western Europe, while warming of bottom waters could destabilize the methane hydrates and result in a major release of greenhouse gasses to the atmosphere. Both the sea-ice distribution and methane hydrate stability in the Arctic Ocean are influenced by its circulation and stratification and in particular by the influx of heat and freshwater from rivers and through its straits.
The purpose of this project is to gain a clearer understanding of what controls the Arctic circulation. Because of the high latitude and strong stratification in the Arctic, the spatial scale of the motions is small (about 10 km) so that a high resolution model is needed to study the circulation here. We will use the Arctic-North Atlantic model developed at L’OCEAN in France which is based on the NEMO (Nucleus for European Modelling of the Ocean) ocean model version 1.9 and the LIM2 ice model. A control run has already been set up on Triolith (under SNIC 2013/11-5) and some sensitivity experiments performed to test the optimal performance of the model (see resources).
We propose to investigate the role of river runoff and transport through Arctic straits on the circulation, stratification, sea-ice distribution, and bottom temperatures of the Arctic Ocean. A series of sensitivity experiments with various freshwater runoff scenarios and various strait flow scenarios are planned and laid out in the request of resources. In the first part, a series of sensitivity runs will be performed to determine the influence of Arctic river runoff on the stratification and circulation. In each of the major river runoff drainage areas (such as the Barents Sea, Laptev Sea, and Kara Sea, and Beaufort Sea) the river flow will be systematically varied from zero to half to one time its current flow. In the second part, we will investigate the importance of the mean flow from the Pacific to Atlantic through the Arctic Ocean. In these experiment we first run the control with the observed flow from the Pacific to the Atlantic, then reduced this flow to zero, and then reverse the flow thought the Arctic. As with the river runoff, the change in stratification and circulation of the Arctic will be studied.
Only in improving our understanding of the control of the present day Arctic circulation do we have hope to predict it in the future or understand it in the past record.